Question: $ { {-3} \times \left[\begin{array}{rr}{4} & {2} \\ {2} & {1}\end{array}\right] = {?} } $
Solution: To multiply a matrix by a number, multiply each item of the matrix by the number. ${\left[\begin{array}{rr}{-3}\times{4} & {-3}\times{2} \\ {-3}\times{2} & {-3}\times{1}\end{array}\right]}$ Now, simplify: ${\left[\begin{array}{rr}{-12} & {-6} \\ {-6} & {-3}\end{array}\right]}$